#include <iostream>
using namespace std;

class b
{
public:
	void f()
	{
		cout << "working function" << endl;
	}
};

class v : public b
{
public:
	virtual void e() =0;
	virtual void f() =0;
protected:
	int i;
};

class a : public v
{
public:
	void e()
	{
		i=5;
		cout << "e implemented" << endl;
	}
	void f()
	{
		cout << "f implemented" << endl;
	}
};

int main()
{
	a t;
	t.f();
	t.e();
	return 0;
}